The present invention relates to a module for use with a portable lathe or the like to machine an area of a pipe to remove irregularities from the area. More specifically, the module is utilized to machine the crown of the weld attaching adjacent ends of pipes together.
It is well known in the art to fabricate pipe lines or piping systems by welding the ends of lengths of pipe together. Typically, the ends of the pipe lengths are bevelled, brought into contact with each other and welded together by running a weld bead around the bevelled end portions. As is also typical, the finished weld bead has a crown portion that extends radially outwardly beyond the peripheries of the adjacent pipe segments. It is necessary, in certain circumstances, to remove this weld crown so that the pipe ends are joined by a smooth, flat surface.
Normally, this task is accomplished by a portable lathe. Such portable lathes typically comprise a stationary power unit, having a rotatable cutting ring and a tool holder to attach a cutting tool to the cutting ring. The portable lathe is attached to one of the pipes and the cutting tool is rotated about the pipe axis and traversed along the axis to remove the weld crown.
This task becomes much more difficult when the adjacent ends of the pipe length are not precisely aligned, but are slightly offset as they are in most applications. It then becomes necessary to support the cutting tool such that the orientation of the axial path of movement changes as the tool rotates around the circumference of the pipe.
A device for supporting a cutting tool in such a fashion is disclosed in U.S. Pat. 4,586,407 to Nall, which is incorporated herein by reference. Although the device set forth in this patent works remarkably well, the device supporting the cutting tool such that its axial path of travel relative to the pipe may follow the non-aligned contours of the weld crown has proven unduly complex.